New findings from a study supported by the National Institute on Drug Abuse (NIDA), National Institutes of Health suggest that toddlers of women who smoked during pregnancy begin to show a pattern of behavior problems as early as 18-24 months of age. It is the first study to show a link between smoking during pregnancy and child behavior problems in the first years of life.
"We already know that smoking can negatively affect the physical health of children," said Elias A. Zerhouni, M.D., NIH Director. "This study tells us we should also be taking a closer look at how it affects development and behavior."
"This study highlights the importance of better understanding how prenatal exposure to nicotine affects the development of the fetal brain, and how in turn this disrupts behavior later on in childhood and adolescence," said Nora Volkow, M.D., NIDA Director. "If we can pinpoint what areas of the brain might be most affected by prenatal cigarette smoke exposure, we can better tailor prevention or remedial intervention while children are very young."
The researchers followed 93 toddlers between their first and second birthdays. Forty-seven percent were prenatally exposed to cigarettes. First, researchers examined whether exposed toddlers' behavior patterns differed over time from non-exposed toddlers. Then they tested if cigarette exposure was associated with specific types of disruptive behavior.
The study was designed to delineate between the normal behavior patterns typically seen in the "terrible twos" and more severe behaviors. The researchers found that toddlers exposed to cigarette smoke in utero exhibited higher levels of behavior problems from 12 through 24 months. The level of behavior problems remained relatively stable over time for the non-exposed toddlers, but for the exposed toddlers the problems increased from 18 to 24 months. Additionally, researchers found that nearly all toddlers with behavior problems in the clinical range at age 2 had been exposed to cigarette smoke. They also found that exposure to cigarette smoke was associated with disruptive social behavior. Exposed toddlers were significantly more likely to exhibit aggressive behavior and to stubbornly refuse to follow directions. They were also less likely to seek out and participate in playful social interactions with their mothers.
Researchers also found that exposure to cigarette smoke was associated with social, rather than emotional aspects of early disruptive behavior. For instance, compared to non-exposed toddlers, exposed toddlers were significantly more likely to exhibit aggressive behavior and to stubbornly refuse to follow directions. They were also less likely to seek out and participate in playful social interactions with their mothers. They were not more likely to have difficulty regulating negative emotion.
"Research into the relationship between prenatal smoking and toddler behavior adds a complex new dimension to our portfolio of knowledge of the deleterious effects of smoking," said Vice Admiral Richard Carmona, United States Surgeon General.
This study does not prove whether or not prenatal exposure to cigarettes causes behavior problems, but it does bring us closer to understanding how that exposure affects fetal brain systems that regulate behavior. The study is being published in the July/August issue of the journal Child Development. The finding comes from a study funded by NIDA and conducted by Lauren Wakschlag, Ph.D., and her colleagues at the University of Illinois at Chicago, in collaboration with researchers at the Universities of York (England) and Massachusetts (Boston), and the National Institute of Mental Health.